1. Field of the Invention
The present invention relates to a method for fabricating a thin film device and, more particularly, to a method for fabricating a thin film device through a thin film transfer process that can be utilized as a fabrication technique of a flexible device.
2. Description of the Related Art
In general, a thin film transfer technique is commonly used for a thin film device such as a thin film transistor (TFT), an electronic device, and an optical device such as an organic electroluminescence (EL) device.
The thin film transfer technique generally refers to a technique of forming a required thin film on a preliminary substrate and transferring the thin film onto a permanent substrate to thus fabricate a desired thin film device. The thin film transfer technique can be advantageously used when conditions of a substrate used for film formation and those of a substrate used for the thin film device are different.
For example, in case where a relatively high temperature process is required, like a semiconductor film formation technique, but a substrate used for a device has a low heat resistance or a low softening point or melting point, the thin film transfer technique can be usefully applied. In particular, the thin film transfer technique is much useful for a flexible thin film device.
In the related art flexible device, which needs to have flexibility, an organic substrate such as polymer is used, on which an organic thin film is used as a thin film to form a function part. However, the function part implemented by the organic thin film cannot guarantee high performance, so the function part of the flexible device needs to be implemented by an inorganic substance such as polysilicon (Poly-Si) or oxide thin film. In this case, the high temperature semiconductor film formation technique cannot be directly applied to the flexible substrate, the organic body, so the thin film transfer technique is employed to transfer a thin film made of an inorganic material such as semiconductor on a preliminary substrate.
However, in the thin film transfer technique, a surface separated from the preliminary substrate is provided as an upper surface of the thin film transferred on the permanent substrate, and residues of a sacrificial layer remain on the upper surface, disadvantageously resulting in the necessity of a process of removing the residues of the sacrificial layer to prevent a negative influence on the thin film device.
Meanwhile, generally, the thin film transfer technique requires a cut and paste process. In detail, in order to separate the thin film device, a transferred body, from the initial substrate (also called a ‘donor substrate’), the thin film device is partially fixed on the substrate by using an etching process and taken out by using a stamp or the like, or an acceptor substrate is stacked and then separated from the donor substrate by using a laser lift off (LLO) process. However, these processes are complicated, and deficiency such as stiction and damage of the thin film device is easily generated in the etching and separating process, and the like.
Thus, a method for simplifying the complicated cut-and-paste process and facilitating mass-production is required to be developed to accomplish a mass-productive thin film device fabrication technology.